Traffic congestion wastes time, energy, and causes pollution. Recently, it
has been estimated that congestion produces 3.5 billions hours delay and 5.7
billions gallons of wasted fuel every year in the U.S. Also, traffic congestion
does not allow an efficient usage of the urban roadways. Often the shortest
path is not the fastest one in metropolitan areas, therefore modern GPS
navigators in addition to give wrong fastest path, increase traffic congestion
because they direct vehicles along the same path. One possible remedy to
the congestion is the exploitation of the vehicle-to-vehicle communication.

Vehicles equipped with devices capable of short-range wireless connectiv-
ity can form a particular mobile ad-hoc network, called a “Vehicular Ad-hoc
NETwork” (VANET). The existence of such networks opens the way for a
large range of applications. One of the most important classes of such appli-
cations is related to route planning. Route planning aims to provide drivers
with real-time traffic information, which would require expensive infrastruc-
ture, in the absence of a VANET.

The evaluation of VANET protocols and applications could be made
through real outdoor experiments, which should involve a large number of
nodes, in order to obtain significant results. However, performing such large-
scale experiments is extremely difficult and expensive. Therefore, simulation
is an indispensable tool.

The simulation of the VANETs requires two different components: a
vehicular traffic simulator, capable to provide an accurate mobility model
for the nodes of a VANET, and a network simulator, for simulating the
behavior of a wireless network. Recent studies have proven that the vehicular
mobility model is very important, and it should be well integrated with
the wireless network model, in order to obtain relevant results. The usage
of an inaccurate mobility model, like the popular random waypoint model
(which may work for some mobile ad-hoc networks, but is definitely not
an accurate representation of mobility in a VANET), can lead to erroneous
results. In order to study traffic congestion, combining an existing vehicular
traffic simulator with an existing wireless network simulator is not possible.
Hence, an integrated simulator is needed.

In the proposed work we addressed two goals: (1) we developed an inte-
grated simulator, that can mix vehicular traffic simulator and selected wire-
less network simulator characteristics, and (2) we investigate the behaviour
of some basic communication protocols to avoid traffic congestion. Finally,
the communication protocols are extensively compared by their capability of
reducing traffic congestion.